阅读官方的邮箱与消息队列例程时没有弄懂延时关系

发布于 2022-08-22 15:00:31 浏览：511 订阅该版

在官方的消息队列例程中，用来发送消息的线程2每次循环延时5ms，接收消息的线程1延时50ms，为什么输出语句中显示线程2发送5次后线程1就结束挂起状态实现一次接收呢？
```c
#include <rtthread.h>

/* 消息队列控制块 */
static struct rt_messagequeue mq;
/* 消息队列中用到的放置消息的内存池 */
static rt_uint8_t msg_pool[2048];

ALIGN(RT_ALIGN_SIZE)
static char thread1_stack[1024];
static struct rt_thread thread1;
/* 线程 1 入口函数 */
static void thread1_entry(void *parameter)
{
    char buf = 0;
    rt_uint8_t cnt = 0;

while (1)
    {
        /* 从消息队列中接收消息 */
        if (rt_mq_recv(&mq, &buf, sizeof(buf), RT_WAITING_FOREVER) == RT_EOK)
        {
            rt_kprintf("thread1: recv msg from msg queue, the content:%c\n", buf);
            if (cnt == 19)
            {
                break;
            }
        }
        /* 延时 50ms */
        cnt++;
        rt_thread_mdelay(50);
    }
    rt_kprintf("thread1: detach mq \n");
    rt_mq_detach(&mq);
}

ALIGN(RT_ALIGN_SIZE)
static char thread2_stack[1024];
static struct rt_thread thread2;
/* 线程 2 入口 */
static void thread2_entry(void *parameter)
{
    int result;
    char buf = 'A';
    rt_uint8_t cnt = 0;

while (1)
    {
        if (cnt == 8)
        {
            /* 发送紧急消息到消息队列中 */
            result = rt_mq_urgent(&mq, &buf, 1);
            if (result != RT_EOK)
            {
                rt_kprintf("rt_mq_urgent ERR\n");
            }
            else
            {
                rt_kprintf("thread2: send urgent message - %c\n", buf);
            }
        }
        else if (cnt>= 20)/* 发送 20 次消息之后退出 */
        {
            rt_kprintf("message queue stop send, thread2 quit\n");
            break;
        }
        else
        {
            /* 发送消息到消息队列中 */
            result = rt_mq_send(&mq, &buf, 1);
            if (result != RT_EOK)
            {
                rt_kprintf("rt_mq_send ERR\n");
            }

rt_kprintf("thread2: send message - %c\n", buf);
        }
        buf++;
        cnt++;
        /* 延时 5ms */
        rt_thread_mdelay(5);
    }
}

/* 消息队列示例的初始化 */
int msgq_sample(void)
{
    rt_err_t result;

/* 初始化消息队列 */
    result = rt_mq_init(&mq,
                        "mqt",
                        &msg_pool[0],             /* 内存池指向 msg_pool */
                        1,                          /* 每个消息的大小是 1 字节 */
                        sizeof(msg_pool),        /* 内存池的大小是 msg_pool 的大小 */
                        RT_IPC_FLAG_PRIO);       /* 如果有多个线程等待，优先级大小的方法分配消息 */

if (result != RT_EOK)
    {
        rt_kprintf("init message queue failed.\n");
        return -1;
    }

rt_thread_init(&thread1,
                   "thread1",
                   thread1_entry,
                   RT_NULL,
                   &thread1_stack[0],
                   sizeof(thread1_stack), 25, 5);
    rt_thread_startup(&thread1);

rt_thread_init(&thread2,
                   "thread2",
                   thread2_entry,
                   RT_NULL,
                   &thread2_stack[0],
                   sizeof(thread2_stack), 25, 5);
    rt_thread_startup(&thread2);

return 0;
}

/* 导出到 msh 命令列表中 */
MSH_CMD_EXPORT(msgq_sample, msgq sample);
```
仿真结果：
```c
\ | /
- RT -     Thread Operating System
 / | \     3.1.0 build Aug 24 2018
 2006 - 2018 Copyright by rt-thread team
msh > msgq_sample
msh >thread2: send message - A
thread1: recv msg from msg queue, the content:A
thread2: send message - B
thread2: send message - C
thread2: send message - D
thread2: send message - E
thread1: recv msg from msg queue, the content:B
thread2: send message - F
thread2: send message - G
thread2: send message - H
thread2: send urgent message - I
thread2: send message - J
thread1: recv msg from msg queue, the content:I
thread2: send message - K
thread2: send message - L
thread2: send message - M
thread2: send message - N
thread2: send message - O
thread1: recv msg from msg queue, the content:C
thread2: send message - P
thread2: send message - Q
thread2: send message - R
thread2: send message - S
thread2: send message - T
thread1: recv msg from msg queue, the content:D
message queue stop send, thread2 quit
thread1: recv msg from msg queue, the content:E
thread1: recv msg from msg queue, the content:F
thread1: recv msg from msg queue, the content:G
…
thread1: recv msg from msg queue, the content:T
thread1: detach mq
```

1 个回答

sync 2022-08-22

这家伙很懒，什么也没写！

我实际测试了下，F407的板子
发送和接收中加入了rt_tick_get的打印
线程2里面的rt_thread_mdelay(5) 时间是不准确的
实际结果如下：
```C
 \ | /
- RT -     Thread Operating System
 / | \     4.0.2 build Sep  1 2021
 2006 - 2019 Copyright by rt-thread team
msh >
msh >
msh >ms
msgq_sample
msh >msgq_sample
msh >thread2: send message - A 4557
thread1: recv msg from msg queue, the contthread2: send messageent:A 4561
 - B 4565
thread2: send message - C 4574
thread2: send message - D 4582
thread2: send message - E 4590
thread2: send message - F 4598
thread2: send message - G 4606
thread2: send message - H 4614
thread1: recv msg from msg queue, the contthread2: seent:B 4618
nd urgent message - I 4622
thread2: send message - J 4631
thread2: send message - K 4639
thread2: send message - L 4647
thread2: send message - M 4655
thread2: send message - N 4663
thread2: send message - O 4671
thread1: recv msg from msg queue, the content:I 4674
thread2: send message - P 4683
thread2: send message - Q 4691
thread2: send message - R 4699
thread2: send message - S 4707
thread2: send message - T 4715
message queue stop send, thread2 quit
thread1: recv msg from msg queue, the content:C 4729
thread1: recv msg from msg queue, the content:D 4784
thread1: recv msg from msg queue, the content:E 4839
thread1: recv msg from msg queue, the content:F 4894
thread1: recv msg from msg queue, the content:G 4949
thread1: recv msg from msg queue, the content:H 5004
thread1: recv msg from msg queue, the content:J 5059
thread1: recv msg from msg queue, the content:K 5114
thread1: recv msg from msg queue, the content:L 5169
thread1: recv msg from msg queue, the content:M 5224
thread1: recv msg from msg queue, the content:N 5279
thread1: recv msg from msg queue, the content:O 5334
thread1: recv msg from msg queue, the content:P 5389
thread1: recv msg from msg queue, the content:Q 5444
thread1: recv msg from msg queue, the content:R 5499
thread1: recv msg from msg queue, the content:S 5554
thread1: recv msg from msg queue, the content:T 5609
thread1: detach mq

msh >ps
thread   pri  status      sp     stack size max used left tick  error
-------- ---  ------- ---------- ----------  ------  ---------- ---
tshell    20  running 0x000000d0 0x00001000    15%   0x00000006 000
tidle0    31  ready   0x0000005c 0x00000100    51%   0x00000015 000
timer      4  suspend 0x0000007c 0x00000200    24%   0x00000009 000
main      10  suspend 0x000000bc 0x00000800    14%   0x00000014 000
```

planetx 2022-08-22

这家伙很懒，什么也没写！

sync 2022-08-22

这家伙很懒，什么也没写！

sync 2022-08-22

这家伙很懒，什么也没写！

把线程2的
延时 rt_thread_mdelay(5)修改为 rt_thread_mdelay(2)
实际如下
```C
 \ | /
- RT -     Thread Operating System
 / | \     4.0.2 build Sep  1 2021
 2006 - 2019 Copyright by rt-thread team
msh >ms 
msgq_sample
msh >msgq_sample
msh >thread2: send message - A 4006
thread1: recv msg from msg queue, the content:Athread2: send message 4009
 - B 4014
thread2: send message - C 4019
thread2: send message - D 4024
thread2: send message - E 4029
thread2: send message - F 4034
thread2: send message - G 4039
thread2: send message - H 4044
thread2: send urgent message - I 4049
thread2: send message - J 4054
thread2: send message - K 4059
m msg queuend messagethread1: recv msg from msg queue, the content:I 4066
thread2: send message - M 4074
thread2: send message - N 4079
thread2: send message - O 4084
thread2: send message - P 4089
thread2: send message - Q 4094
thread2: send message - R 4099
thread2: send message - S 4104
thread2: send message - T 4109
message queue stop send, thread2 quit
thread1: recv msg from msg queue, the content:B 4122
thread1: recv msg from msg queue, the content:C 4177
thread1: recv msg from msg queue, the content:D 4232
thread1: recv msg from msg queue, the content:E 4287
thread1: recv msg from msg queue, the content:F 4342
thread1: recv msg from msg queue, the content:G 4397
thread1: recv msg from msg queue, the content:H 4452
thread1: recv msg from msg queue, the content:J 4507
thread1: recv msg from msg queue, the content:K 4562
thread1: recv msg from msg queue, the content:L 4617
thread1: recv msg from msg queue, the content:M 4672
thread1: recv msg from msg queue, the content:N 4727
thread1: recv msg from msg queue, the content:O 4782
thread1: recv msg from msg queue, the content:P 4837
thread1: recv msg from msg queue, the content:Q 4892
thread1: recv msg from msg queue, the content:R 4947
thread1: recv msg from msg queue, the content:S 5002
thread1: recv msg from msg queue, the content:T 5057
thread1: detach mq

```